Optical sensing arrays employing misaligned squint optical ones with offset emitters and detectors compared to aligned axes

Abstract

An optical sensing array and method of operation for controlling the acceptance angle of light beams which are iteratively strobed in side-by-side channels between light transmitters and light receivers. In one embodiment, the light beams in at least a pair of channels are directed along axes which are intentionally mispointed or squinted. A control circuit measures the amplitudes of signals produced responsive to light being received by the light receivers and compares the ratio of those amplitudes to the ratio of predetermined high and low amplitude values which provide a threshold window. When the ratio of the signal amplitudes exceeds the ratio of the window threshold values, an output signal is produced indicative of an unsafe operating condition. The control circuit further maintains the gain of the signals from the light receivers to stay within the range of the predetermined window threshold values. In another embodiment, the light transmitter and receiver in at least one channel are offset in opposite directions from an optical axis of the channel for producing a narrow beam angle.

What is claimed is: 
     
       1. A method of operating an optical sensing array in which light beams are strobed from a plurality of light transmitters in side-by-side channels toward a plurality of light receivers which are associated with respective channels and are adapted to sense the light beams for producing output signals, and in which an optical axis extends between the transmitter and receiver of each channel, the method comprising the steps of squinting the light beam being strobed from the light transmitter in at least one of the channels on one side of said optical axis, squinting the light receiver in said one channel on a side of said optical axis which is opposite said one side and producing an output signal responsive to light being received by the light receiver. 
     
     
       2. A method as in claim 1 in which the step of squinting the light beam being strobed from the light transmitter is carried out by offsetting the light transmitter at a predetermined distance from and in a given direction from the optical axis in said one channel, and the step of squinting the light receiver is carried out by offsetting the light receiver a predetermined distance from and in a direction which is substantially opposite said given direction. 
     
     
       3. In an optical system in which light beams are strobed from a plurality of light transmitters in side-by-side channels toward a plurality of light receivers which are associated with respective channels and are adapted to sense the light beams for producing output signals, and in which an optical axis extends between the transmitter and receiver of each channel, an optical sensing array comprising the combination of light transmitter means having a light transmitter in each channel for strobing the light beam, light receiver means having a light receiver in each channel for sensing light, first squinting means for squinting the light beam being strobed from the light transmitter in at least one of the channels in a first direction on one side of said optical axis, second squinting means for squinting the light receiver associated with said one channel in a second direction on a side of said optical axis which is opposite said one side, and means for producing an output signal responsive to the sensing of light by said light receiver means. 
     
     
       4. An optical sensing array as in claim 3 in which first squinting means includes means for offsetting the light transmitter at a predetermined distance from and in a given direction from the optical axis in said one channel, and said second squinting means includes means for offsetting the light receiver a predetermined distance from and in a direction which is substantially opposite said given direction in said one channel. 
     
     
       5. A method of operating an optical sensing array for controlling the acceptance angle of light beams which are iteratively strobed in cycles from a plurality of light transmitters in side-by-side channels toward a plurality of light receivers which are associated with respective channels and are adapted to sense the light beams for producing signals, and in which an optical axis extends between the transmitter and receiver in the channels, the method comprising the steps of directing the light beam in a first one of the channels along a first axis which is squinted relative to a second axis along which the light beam in at least a second one of the channels is strobed, squinting the light beam being strobed from the transmitter in at least a selected channel on one side of said optical axis, squinting the light receiver in said selected channel on a side of said optical axis which is opposite said one side, producing a signal V 1  responsive to light being sensed by the light receiver associated with the first channel, producing a signal V 2  responsive to light being sensed by the light receiver associated with the second channel, establishing a predetermined high amplitude value V H , establishing a predetermined low amplitude value V L  which is below V H , comparing the ratio V 1  /V 2  to a ratio V H  /V L , and producing an output signal responsive to V 1  /V 2  >V H  /V L . 
     
     
       6. An optical sensing array system for controlling the acceptance angle of light beams, the system comprising the combination of a light transmitter having a plurality of light transmitter elements, a light receiver having a plurality of light receiving elements which are arrayed across a protected zone from respective ones of the light transmitter elements, means for iteratively strobing light beams from the light transmitter elements in side-by-side channels toward the light receiver elements, each channel including an optical axis extending between the light transmitter and receiver elements, beam squinting means for causing the light beam in a first one of the channels to be directed toward the respective light receiving element in the first channel. along a first axis which is squinted relative to a second axis along which the light beam in at least a second one of the channels is strobed, said beam squinting means including first squinting means for squinting the light beam being strobed from the light transmitter and at least a selected one of the channels in a first direction on one side of said optical axis and second Squinting means for squinting the light receiver element associated with said selected channel in a second direction on a side of said optical axis which is opposite said first side, means for producing a signal V 1  responsive to light being sensed by the light receiver element of the first channel, means for producing a signal V 2  responsive to light being sensed by the light receiver element of the second channel, means for establishing a predetermined high amplitude value V H  and a predetermined low amplitude value V L  which is below V H , means for comparing the ratio V 1  /V 2  to the ratio V H  /V L , and means for producing an output signal responsive to V 1  /V 2  >V H  /V L .